The present invention concerns a payout device for data transmission lines according to the preamble of patent claim 1, as well as a method for the production of a payout device for data transmission lines.
Payout devices for data transmission lines find application in movable objects that can be remotely controlled, such as, for example, rockets missiles, aircraft as well as in land vehicles, water vehicles and underwater devices, which will be steered over great distances from a base station with the help of a data transmission line. Thus the data transmission line is withdrawn at a high speed, which can sometimes even reach supersonic speed, from at least one coil or spool or a spool system.
For example, an aircraft can be steered and controlled, e.g., by electrical signals via a direct wire connection between the aircraft and an earth station Thus a rule, strain-relieved Cu twin conductor lines are used, whereby the disadvantage arises, however, that only low-frequency signals can be transmitted over a relatively short distance.
Optical signals of high bandwidth can be transmitted over great distances by the use of fiber-optic waveguides as data transmission lines. So-called monomodal optical waveguides have already come close to the theoretical minimum attenuation. Thus, the necessary data can be transmitted over more than 100 km by means of optical devices. The fiber-optic waveguide normally used as the data transmission line is comprised essentially of a glass substrate, which is surrounded by a coating or plastic protective layer. The coating may comprise one or more layers of different types of plastic, whereby normally very soft types of plastic, such as, e.g., polyacrylate, are used. The coating serves for protection of the glass substrate from physical and chemical influences and reduces micro-bending, i.e., the attenuation of the light that passes through the optical waveguide as a consequence of partial pressure on the optical waveguide.
The data transmission line is wound onto a spool unit as a coil package in a known device. Several layers of windings are introduced under tensile stress and glued together. The tensile stress or the winding tension is necessary in order to endow the coil package with a high stability, which is necessary in the case of rapid unwinding, e.g., by a rocket. On the other hand, there is the danger that several layers are pulled off simultaneously and form a loop, which leads to the breakdown of the data transmission line. Data transmission lines of plastic or with a plastic protective layer, which are wound on a spool as a coil package, however, have the disadvantage that the plastic or the coating shows a great tendency for creep or flow behavior under the indicated stress. In this way, a deviation from linear force-deformation behavior is produced. Under the pressure of the windings, macromolecules and molecular chains are rearranged, so that a viscous behavior of the material results. Moreover, the windings of the coil package loosen over the course of time and disruptions arise in the arrangement of the coil package. Individual windings become crooked and during the unwinding operation, there is the increased danger that the windings will be pulled off irregularly and form loops, which will lead to breaking.
It is thus proposed in FR 2,644,764 A1 that the number of [winding] layers on a spool will not be greater than 40. Thus a spool system is shown, which is comprised of several spools, each of which does not have more than 40 windings, The limitation to 40 layers will prevent excessive creep of the coating, so that no relative shifts of the windings with respect to one another will occur and the order of the winding is retained. The construction proposed therein, however, has the disadvantage that a multiple number of spools must be integrated into one system and connected together, which is very expensive, and which has as a consequence additional components and thus additional weight, and requires a precise adjustment in the interplay of the spools.
It is thus the object of the present invention to provide a payout device for data transmission lines, by means of which the stability of a coil package with very many layers of windings is retained even over a long period of time, with relatively little expenditure. In addition, a method is proposed, which can be conducted in a cost-favorable manner, and-will make possible the production of a stable and secure payout device for data transmission lines with long lengths.
The payout device for data transmission lines according to the invention, which serves for the transmission between a moving object and a station, has a spool unit, on which a data transmission line is wound in the form of a package of several layers of windings, whereby the windings in each layer are introduced with a maximum tensile stress or tensile force, which is dependent on the modulus of elasticity of the data transmission line that is used. In this way, it is achieved that the windings show no creep or flow, which adversely affects the stability of the winding, whereby the windings remain stable in their position over a long period of time. The defined tensile stress of the windings is thus just high enough that a slipping of the windings is prevented even in the case of the indicated external influences and no disruptive creep occurs. The spool according to the invention may be produced by machine in a cost-favorable manner and with a defined tensile stress, whereby the tensile stress can be easily adapted to the respective material of the optical waveguide used.
Preferably, the maximal tensile stress is calculated according to formula Fmax less than a+bxc2x7E, whereby a and b depend on the diameter of the data transmission line and/or the diameter of the spool unit, and E is the modulus of elasticity of the data transmission line. The maximum tensile stress is calculated particularly from the diameters of the data transmission line and the spool unit, the modulus of elasticity of the data transmission line and the total number of layers in the package.
Advantageously, the pressure of a winding on the layers that lie underneath it is less than 0.6 N/mm2, at least in the lower region of the package. The windings in the package may be introduced with a winding tension, which is increased linearly from one layer to the next.
Preferably, the maximum tensile stress is calculated according to the formula       F    max     less than             0.3      ⁢              xe2x80x83            ⁢              N                  mm          2                    ⁢              xe2x80x83            ⁢                        d          ⁡                      (                                          d                ·                N                            +                              D                s                                      )                          N              +                  E        ·                  d          E          3                            3        ⁢                  D          s                    
wherein d is the diameter of the data transmission line in mm, DS is the diameter of the spool unit in mm, N is the total number of layers of the package, E is the modulus of elasticity of the data transmission line in N/mm2 and dE is the diameter in mm of the material of the data transmission line, which is relevant for the modulus of elasticity.
The maximum tensile stress of the nth winding can be calculated according to the formula:       F    max    ≤                              1          ⁢                      xe2x80x83                    ⁢          Newton                N            ⁢      n        +          0.3      ⁢              xe2x80x83            ⁢              Newton                  mm          2                    ⁢              xe2x80x83            ⁢                                    d            ⁡                          (                                                D                  s                                -                                  N                  ·                  d                                            )                                N                ⁡                  [                      1            -                          xe2x80x83                        ⁢                          n              N                                ]                      +                  E        ·                  d          E          3                            3        ⁢                  D          S                    
wherein n is the respective layer number, N is the total number of layers of the package, d is the diameter of the data transmission line in mm, DS is the diameter of the spool unit in mm, E is the modulus of elasticity of the data transmission line in N/mm2, dE is the diameter in mm of the material of the data transmission line, which is relevant for the modulus of elasticity.
Advantageously, the data transmission line is a monomodal optical waveguide with one or more plastic layers, which is preferably wound onto the spool unit at a tensile force of less than or equal to 0.4 N. The windings can be glued with an elastic adhesive.
In the method according to the invention for the production of a payout device for data transmission lines, a spool unit with a data transmission line is wound such that several layers of windings form a coil package on the spool unit, whereby the windings in each layer are introduced at a maximum tensile stress or tensile force, which is dependent on the modulus of elasticity of the data transmission line. In this way, a coil package that is stable over a long period of time can be produced in a simple way and with conventional components.
Advantageously, a payout device as is described above, is produced by the method according to the invention. Preferably, after winding onto the spool unit, a temperature treatment is conducted at a temperature higher than 35xc2x0 C., whereby the duration of the temperature treatment advantageously amounts to 8 hours and more.